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ICSE Class 10 Chemistry Question 21 of 69

Study of Compounds — Ammonia — Question 15

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Question

Question 15

Distinguish between the following (using ammonia solution) :

(a) Calcium chloride and zinc chloride.

(b) Ferric salt and ferrous salt

(c) Zinc nitrate and lead nitrate

Answer

(a) When we add ammonium hydroxide solution to both the given salt solutions, Zinc Chloride reacts to form a gelatinous white precipitate of Zinc Hydroxide (ZnOH), whereas, no such observations i.e no precipitate will form in case of Calcium Chloride solution because ammonium hydroxide is a weak base and it cannot react with calcium salts to precipitate the hydroxide of calcium.

ZnCl2 + 2NH4OH ⟶ Zn(OH)2 + 2NH4Cl

(b) On reaction with ammonium hydroxide, Iron [II] sulphate (ferrous salt) forms a dirty green ppt whereas iron [III] sulphate (ferric salt) forms a reddish brown ppt. Hence, the two can be distinguished easily.

FeSO4 + 2NH4OH ⟶ (NH4)2SO4 + Fe(OH)2 ↓

Fe2(SO4)3 + 6NH4OH ⟶ 3(NH4)2SO4 + 2Fe(OH)3 ↓

(c) When zinc nitrate is treated with ammonium hydroxide, white gelatinous ppt. of Zinc hydroxide is formed which is soluble in excess of NH4OH.

Zn(NO3)2 + 2NH4OH ⟶ 2NH4NO3 + Zn(OH)2 ↓

Whereas, when lead nitrate is treated with ammonium hydroxide, white ppt. of lead hydroxide is formed which is insoluble in excess of NH4OH

Pb(NO3)2 + 2NH4OH ⟶ 2NH4NO3 + Pb(OH)2 ↓